PROJECT ABSTRACT E-cigarette, or vaping, associated lung injury (EVALI) is a new, serious respiratory disease of uncertain cause, treatment, and clinical outcome. Despite progress in case identification and characterization of the early course, there are key questions related to the longer-term consequences for individuals with EVALI and the pathobiologic mechanisms that lead to acute respiratory failure. Intermountain Healthcare and the University of Utah have been actively engaged in studies of EVALI from the early stages of this outbreak, and together we are well-positioned to address both of these important questions. We have established a cohort of over 140 EVALI patients and have described the case presentation and response to therapy. We have provided initial information concerning the distinct appearance of alveolar macrophages (AM) in these individuals. We now propose to address clinical and pathobiologic questions concerning EVALI in experiments with two Specific Aims. In Specific Aim 1, we will leverage our research infrastructure, experience in short- and long-term clinical studies of acute respiratory distress syndrome (ARDS) as part of the PETAL network, and experience with EVALI to assess the long-term clinical outcomes of patients with EVALI. We will use electronic health record queries to assess changes in healthcare use and respiratory illnesses in the year before vs. after an EVALI diagnosis in the entire cohort of over 140 patients and how those may be influenced by comorbidities. Using validated instrument batteries, we will assess 80 individuals at 3 and 12 months after initial hospitalization for EVALI to determine: (a) the presence and persistence of respiratory impairment at 12 months after EVALI, (b) whether residual respiratory symptoms evolve between 3 and 12 months after EVALI, (c) the distribution of recurrent vaping among EVALI survivors, including changes in devices or cartridges and implications of baseline mental illness, (d) the association of recurrent vaping with respiratory impairment, and (e) changes in healthcare use and respiratory illnesses in the year before vs. after an EVALI diagnosis. Multiple characteristics of the acute illness suggest that AM inflammatory responses play an important role in the pathogenesis of EVALI. In Specific Aim 2, we will compare bronchoalveolar lavage (BAL) samples from 10 patients with EVALI to those in 10 ?healthy? vapers. Using RNA-seq we will identify pathways in differentially activated EVALI subjects compared to individuals who vape without evidence of EVALI. We will also use flow cytometry to determine the ontogeny and additional activation features of AM in these two groups, and will determine the extent of alveolar epithelial cell injury in analysis of the cell-free supernatant from BAL samples. This proposed work aims to answer the crucial, complementary questions to shed further insight into the pathophysiology and outcomes of EVALI. Furthermore, insights from this work will add to our evolving understanding of the risks associated with vaping, prepare us for potential future outbreaks associated with e- cigarette use, and advance our understanding of the molecular mechanisms of acute lung injury in general.